Hi,
I am using treemap with nest transform and in the resulting data i can see aggregate values for each key generated if i check root object. However i am not able to access the same in vega datum object for each node.
Docs state: The sum of values for a node and all its descendants is available on the node object as the value property.
It would be helpful to have a way to get these values in vega if not already there.

I asked the same question in google groups thread with more details and example. Here's the link address:
https://groups.google.com/forum/#!topic/vega-js/jvdqLbYLItQ